Abstract Electron spin resonance ESR spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane 2-methylpropane hydrate prepared with deuterated water were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this -hydrogen picking- process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ-mol, which was in agreement with the activation energy 39 ± 5 kJ-mol of hydrogen picking in the γ-ray-irradiated propane hydrate with deuterated water. View Full-Text